1. Technical Field
The present disclosure relates to a power transmission device which is provided in a vehicle. In particular, the present disclosure relates to improvement of a configuration for suppressing rattling noise caused by a backlash on the power transmission path.
2. Description of Related Art
It is known that rattling noise occurs due to collision between teeth facing each other with a backlash between rotary shafts constituting a power transmission device provided in a vehicle, and measures to suppress rattling noise are suggested. For example, in a power transmission device of International Publication No. WO 2013/080311 (WO 2013/080311 A), a rotor shaft of a second electric motor constitutes a part of a power transmission path from an engine to drive wheels. Accordingly, since the directly transmitted torque of the engine is transmitted to the rotor shaft, even if the torque of the second electric motor is nearly zero, and during driving of the engine, a spline tooth of the rotor shaft is pressed against a spline tooth of the other rotary shaft. Accordingly, a backlash between the spline tooth of the rotor shaft and the spline tooth of the other rotary shaft is eliminated, and rattling noise is suppressed.
On the other hand, in the power transmission device of WO 2013/080311 A, while a backlash on an upstream side (engine side) of the rotor shaft of the second electric motor on the power transmission path can be eliminated, a backlash which is formed between an input shaft of a transmission arranged on a downstream side (drive wheel side) of the second electric motor and the rotor shaft of the second electric motor cannot be eliminated. Accordingly, if torque which is input to the transmission becomes nearly zero, rattling noise due to a backlash formed between the rotor shaft of the second electric motor and the input shaft of the transmission may occur.
As measures to suppress rattling noise, a case where a tolerance ring is provided between the rotor shaft of the second electric motor and the input shaft of the transmission, and relative rotation of the rotor shaft of the second electric motor and the input shaft of the transmission is regulated is considered. That is, a case where the tolerance ring is interposed between the rotor shaft and the input shaft, and in a situation in which input torque to the input shaft does not exceed a predetermined value, the rotor shaft and the input shaft are rotated integrally by the tolerance ring is considered.